PROJECT TITLE :

Numerical simulation on molecular displacement and DC breakdown of LDPE

ABSTRACT:

It is generally known that the dc breakdown strength of low density polyethylene (LDPE) decreases with because the thickness and temperature of the sample increase. The breakdown strength is influenced by the charge transport and electrical field distortion, and is also connected to the molecular chain displacement and fracture. This paper investigates mutual relations among the charge transport, molecular chain displacement, and thickness dependent dc breakdown of LDPE. A model that mixes the dynamics of charge transport and molecular displacement (CTMD) is used to calculate the house charge accumulation, molecular chain displacement, and dc breakdown properties of LDPE with numerous thicknesses at varied constant voltage ramping rates. It's assumed that breakdown happens when the molecular chain displacement reaches a vital worth. The simulation results show that the breakdown field as a operate of sample thickness satisfies an inverse power law with an influence index of about 0.forty three for varied voltage ramping rates. This can be per experimental results. The CTMD model considers each the distortion of electrical field and therefore the displacement kinetics of molecular chains, resulting in a power index nearer to the experiment than that calculated solely from the electrical field distortion. Adopted a Williams-Landel-Ferry sort molecular chain mobility in the CTMD model, the simulation results are per the results calculated by applying experimental results on polyisobutylene and polymethyl methacrylate to the free volume breakdown theory. It's conjointly found that the CTMD model with temperature-dependent molecular chain mobility controlled by piecewise Arrhenius equations will justify well the temperature dependent breakdown experimental results of LDPE.